You’ve probably already mad a decision for your gravel PM by now but I thought I’d mention it anyway. I have a P2M NGeco on my MTB with the same rubber batter cover and it has never been an issue. I’ve ridden hundreds of hours on it in the past 18 months and have never even thought about it, let alone lose it.
Reckon you could run these with an InfoCrank
I ended up buying the 46/30 P2M NGeco gravel cranks and my partner now has my Rotor w/ P2M on her road bike.
I know someone who lost their NGeco cover and another person that zipties their’s on (not sure if they’d lost one already or not). It depends what sort of terrain you ride. My “gravel” bike has been finding its way onto some MTB trails so when I bail on stuff I can swipe my foot across the crank, so I can understand how you could knock the cover off. I’ve not lost it yet though. Touch wood.
I added a spare cover to my initial order from them but I should pull a finger out and add that zip tie backup.